The counterfeiting of standardized documents such as passports and credit cards is a continuing problem. Even though credit cards and money cards generally carry magnetically readable stripes, they can easily be counterfeited. Drivers licenses commonly are laminates bearing a photograph beneath a transparent covering and also are easy to counterfeit. Some drivers licenses have been made more difficult to counterfeit by incorporating a legend which becomes visible only under retro-reflective viewing conditions as disclosed in U.S. Pat. No. 3,801,183 (Sevlin et al.). The same retro-reflective system has been used on phonograph labels. Even so, a need has continued for inexpensive techniques for making counterfeiting of standardized documents more difficult without appreciably adding to the cost of the documents or requiring expensive verifying equipment.